LTC3589 datasheet(30/50 Pages) LINER

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LTC3589/LTC3589-1/

LTC3589-2

3589fe

OPERATION

power-up state (PUP) until ON is held LOW for at least

400ms (PB400ms) or until PWR_ON is activated by the

PWR_ON pin. When the controller enters the PUP state

the open-drain WAKE pin releases HIGH. The WAKE pin

is typically used to enable the first regulator in a start-up

sequence. The pushbutton state will stay in PUP for five

seconds before transitioning to the power-on (PON) state.

Before leaving PUP, the PWR_ON pin must be brought

HIGH by the application to indicate that the system rails

are correct. If PWR_ON is not active at the end of five

seconds the pushbutton controller will continue directly

through PON to the power-down (PDN) state and pull the

WAKE pin down. Three events will cause the pushbutton

to leave the PON state: 1) lowering the PWR_ON pin, 2)

forcing a hard reset by holding the ON pin LOW for five

seconds, and 3) a fault condition is detected. Fault condi-

tions are low VIN, device over temperature, or extended

undervoltage of one of the regulator outputs. All regulator

enables, the ON input, and PWR_ON signals are inhibited

for one second while in the PDN state. After one second

in PDN the pushbutton controller returns to POFF.

PBSTAT Operation

PBSTAT goes LOW 50ms after the initial pushbutton ap-

plication (ON LOW) and will stay LOW for a minimum of

50ms. PBSTAT will go HIGH coincident with ON going HIGH

unless ON goes HIGH before the 50ms minimum on-time.

Power-Up Using the Pushbutton

When in the POFF standby state, the LTC3589 is in com-

plete shutdown except the always active LDO1 and any

regulators enabled with the keep-alive control bits. Pull the

ON pin to ground with a pushbutton for 400ms to begin a

power-up sequence with the WAKE pin tied to an enable

pin. Drive PWR_ON high within five seconds to signal the

LTC3589 to remain in the power-on state.

Power-Down Using the Pushbutton

The pushbutton power-down operation is performed by

the system microprocessor by monitoring the PBSTAT pin.

Once in the PON state, the system controller is responsible

for deciding what action to take with a pushbutton event.

When the ON pin is held LOW for a 50ms debounce period,

the PBSTAT pin is pulled LOW. The system controller should

monitor the PBSTAT pin to determine the pushbutton has

been pushed. If the controller decides that a power-down

is desired, then it should drive the PWR_ON pin LOW.

Power-Up and Down Using PWR_ON Pin

An alternate power-up method is to drive the PWR_ON pin

to a HIGH state. After a delay of 50ms from the PWR_ON

signal, the WAKE pin will pull HIGH to drive regulator en-

able pins. When PWR_ON is HIGH for five seconds, the

sequence controller will enter the PON state. To power

down, drive the PWR_ON pin LOW. 50ms later WAKE will

pull low, all enabled regulators are disabled and the OVEN

command register is reset to 0x00.

Hard Reset Using the Pushbutton

When the ON pin is pulled LOW for five seconds, a hard

reset is initiated. At the end of five seconds, WAKE is

pulled LOW, the I2C command registers are reset to POR

states, enable pin states are ignored, and the one second

power-down timer is started. During the power-down time,

the enables continue to be ignored to allow the regulator

outputs to discharge. The RSTO pin is pulled LOW for

the power-down time to indicate a pushbutton hard reset

occurred. If the PWR_ON pin is LOW at the end of the

one second power-down time, the LTC3589 will remain

in standby mode. If PWR_ON is HIGH at the end of one

second and there are no fault conditions, the LTC3589 will

power-up in the same way shown in Figure 8.

Hard Reset Due to a Fault Condition

A hard reset due to VIN undervoltage, extended undervolt-

age of an output rail, or an overtemperature condition

initiates a hard shutdown of the LTC3589. When the fault

occurs, wake is pulled LOW, the I2C command registers

are reset to POR states, enable pin inputs are ignored,

and the one second power-down timer is started. Dur-

ing the power-down time, the enables continue to be

ignored to allow the regulator outputs to discharge. If the

PWR_ON pin is LOW at the end of the power-down time,

the LTC3589 will remain in standby mode with just the

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